502103 五、發明說明（1 ) i明之領域 本發明是關於一種可從第一流體將熱傳遞到第二流體 之熱交換器，其包括有一或多個第一流體之流路，其被 配置成彼此平行且彼此維持一個距離，並且其外壁是與 第二流體上由金屬發泡形成之流動體做熱傳遞接觸。 先前之枝術說明 ΕΡ-Α- 0 744 586中已揭示一種熱傳遞元件，例如一個 板或管，其具有銅發泡形式之大的熱傳遞表面，而使用 在熱交換器中用來改善熱傳遞。此種元件是使用蒸氣沉 積法，將氧化銅粉末沉積在事先已設置有黏著劑之塑膠 發泡上而製成。依照此方式所製成之此發泡然後在輕度 之壓力下配置在一個板或管上，此一個板或管同樣地事 先覆有氧化銅粉末，因而可由燒結而形成複合元件。在 塑膠發泡之裂解之後，氧化銅被還原成銅。 上述形式之熱交換器被使用在，例如所謂之熱音學之 熱引擎中。在此種熱交換器中第一熱迴路是由通過一般 多數個流路之如氣體或液體的第一流體所形成。第二熱 迴路包括一般爲氣體（氬氣，空氣）通過細孔狀流動體之 第二流體的流動，其流動體在某一個區域圍住流路。第 二流體通過流動體的流動方向一般爲垂直流路中第一流 體的流動方向。細孔狀流動體與流路外壁做熱交換接觸 。熱可從第一流體被傳遞到流路之內壁’並且由於壁材 料之傳導而被攜帶到外壁。在外壁處’到細孔狀流動體 502103502103 V. Description of the invention (1) Field of the invention The present invention relates to a heat exchanger capable of transferring heat from a first fluid to a second fluid, which includes one or more flow paths of the first fluid, which are configured to They are parallel to each other and maintain a distance from each other, and their outer walls are in heat transfer contact with a fluid body formed of metal foam on the second fluid. A previous branch technique description EP-A-0 744 586 has disclosed a heat transfer element, such as a plate or tube, which has a large heat transfer surface in the form of copper foam, and is used in heat exchangers to improve heat transfer. This component is made by depositing copper oxide powder on a plastic foam that has been provided with an adhesive in advance using a vapor deposition method. The foam produced in this way is then placed under a slight pressure on a plate or tube, which is likewise covered with copper oxide powder beforehand, so that a composite element can be formed by sintering. After the plastic foam is cracked, copper oxide is reduced to copper. The above-mentioned heat exchanger is used in, for example, a so-called thermo-acoustic heat engine. In this type of heat exchanger, the first heat circuit is formed by a first fluid, such as a gas or a liquid, which generally passes through a plurality of flow paths. The second thermal circuit includes the flow of a second fluid, usually a gas (argon, air), through a pore-shaped fluid, and the fluid surrounds the flow path in a certain area. The flow direction of the second fluid through the fluid is generally the flow direction of the first fluid in the vertical flow path. The pore-like flow body makes heat exchange contact with the outer wall of the flow path. Heat can be transferred from the first fluid to the inner wall 'of the flow path and carried to the outer wall due to the conduction of the wall material. At the outer wall ’to the pore-like flow body 502103
五、發明說明（2) 之熱傳遞是由輻射及傳導所進行。熱傳導在細孔狀流動 體中產生。當僅有由金屬發泡製成之流動體時，此熱傳 導被限制住，因而有時由具有良好熱傳導性之材料所製 成之固體薄的鰭片被設置在金屬發泡中，以增加熱傳導 。從流動體到第二流體之熱傳遞同樣地由輻射及傳導所 進行。整體之熱傳遞效率視所有這些從流動體到第二流 體之轉移、傳遞而定，反之亦然，一般在氣體側之熱傳 遞尤其可代表爲一項抑制因素。 已發現到雖然使用金屬發泡，選擇性地與薄片或散熱 鰭片結合時，可提供擴大的熱交換表面積，並且可增加 熱傳導，流動阻抗很高，故整體性能以熱傳遞與流動阻 抗之比率表示時，會比僅具有薄片或散熱鰭片之傳統熱 交換器差。在許多情況中，當使用金屬發泡時熱傳遞之 增加往往伴隨著流動阻抗亦成不成比例地增加。 美國專利US-A-4,245,469已揭示一種熱交換器，其中 多孔狀金屬陣列被配置在熱傳遞媒體流動之流路中。據 該文所言，此金屬陣列在垂直於流動方向之區域中有較 大的密度，使內熱傳遞係數在此區域中可被增加，而環 境之溫度則比流路末端者高很多。爲了降低熱傳遞媒體 體積之減少，此現象往往在恆定直徑之通路下產生，在 該區域之位置的直徑被增加。此種設計即著眼於改善內 部熱傳遞。 再者，DE A1 39 06 446已揭示一種熱交換器，其中鋁5. Description of the invention (2) The heat transfer is performed by radiation and conduction. Heat conduction occurs in the pore-like fluid. When there is only a fluid body made of metal foam, this heat conduction is limited, so sometimes solid thin fins made of a material with good thermal conductivity are placed in the metal foam to increase the heat conduction . The heat transfer from the fluid to the second fluid is likewise carried out by radiation and conduction. The overall heat transfer efficiency depends on all these transfers and transfers from the fluid to the second fluid, and vice versa. Generally, the heat transfer on the gas side can represent a suppressing factor. It has been found that although metal foam is used, when selectively combined with a sheet or a heat sink fin, it can provide an enlarged surface area for heat exchange, increase heat conduction, and have high flow resistance. Therefore, the overall performance is based on the ratio of heat transfer to flow resistance It is worse than a traditional heat exchanger with only thin sheets or fins. In many cases, the increase in heat transfer when metal foaming is used is often accompanied by a disproportionate increase in flow resistance. U.S. Patent No. US-A-4,245,469 has disclosed a heat exchanger in which a porous metal array is arranged in a flow path in which a heat transfer medium flows. According to the article, the metal array has a higher density in the area perpendicular to the flow direction, so that the internal heat transfer coefficient can be increased in this area, and the temperature of the environment is much higher than that at the end of the flow path. In order to reduce the decrease in the volume of the heat transfer medium, this phenomenon often occurs under a constant-diameter path, and the diameter of the position in the region is increased. This design is aimed at improving internal heat transfer. Furthermore, DE A1 39 06 446 has disclosed a heat exchanger in which aluminum
-4- 502103 五、發明說明（3) 發泡被配置在流路之中。右需要的話，在此發泡中之細 孔尺寸可改變，即細孔之數目可變化。 發明之扼要說明 本發明之一般目的在改善整體性能，即上述一個熱交 換器之熱傳遞與流動阻抗之間的關係。 在上述型式熱交換器之中，依照本發明之金屬發泡具 有金屬體積密度上之梯度。此具有金屬體積密度上之梯 度的金屬發泡之使用’使發泡之體積密度，即金屬之量 在細孔數目（PPI )仍維持相同之時可適合於地區之熱通量 密度及流動阻抗。在金屬發泡中，熱通量密度在流路附 近中爲最高，使金屬發泡在此位置必須比流動體之外周 含有更多之金屬，而其熱通量密度卻低很多。這是由於 所使用金屬發泡之金屬體積密度被改變之故。依照本發 明，其熱交換器之金屬發泡的配置，具有促進從金屬發 泡到流路之壁的熱傳遞之效果。PPI維持相同時，在分隔 細孔的金屬肢厚度維持相同之時，金屬發泡中之金屬體 積梯度比變化細孔之數目更有效果。 此種具有體積密度梯度之金屬發泡，例如由在電解槽 中在塑膠發泡上進行電鍍之電鍍法而可被製成，下面將 詳細解釋。 須提及者，FR-A- 2 766 967專利中已揭示一種電子元 件用之散熱座（heat sink)，其包括有一種金屬發泡具 有沉積金屬，其在發泡之厚度方向上具有厚度之梯度 502103 五、發明說明（4) (gradient)。 因爲在此種生產方法中，發泡密度在一個方向上變化 ，流動體最好包括有至少兩層金屬發泡，其具有相同體 積密度之層表面彼此互相面對。此可使得流動體許多實 施例具有應用上之優點。 在第1實施例中，金屬發泡之體積密度從第二流體之 流動體之流入側朝向流路增加，使更多金屬會在熱通量 密度較大之處產生。 流路之形狀並非絕對重要，圓形管，平坦中空管等均 可使用。但是，爲了限制流動阻抗，流路之形狀最好配 合到第二流體之流動形狀。流路爲橢圓形剖面時很有利 ，其主軸向第二流體之流動方向延伸。此種形狀之流路 可結合一個具有低流動阻抗之大熱交換表面積。 流動體然後有利地包括兩層金屬發泡，最好其在每線 性之英吋上（PPI )具有相同數目之細孔，其中具有最高金 屬體積密度之側面彼此互相面對。在這些側上，設置有 流路上之凹處。 依照另一個較佳實施例，特別是其簡單之模組化構造 很有利，流路包括矩形剖面之管狀體，並且其由流動體 之部份所分離，流動體之部份的體積密度，在流路之外 壁附近爲最高。此熱交換器之較佳實施例的模組可包括 ，例如爲矩形剖面之此種流路，其兩個相對壁設置有一 層金屬發泡，其中具有最高體積密度之層表面與討論中 502103 五、發明說明（5) 之壁結合。 若熱交換器更類似於一種具有流動 體包含 有 由 薄 片 所 隔開之金屬發泡部分之熱交換器時最 爲期望 者 可 使 用 多數個層之金屬發泡，其體積密度之 梯度平 行 於 第 一 流 體之流動方向，最好爲成交互狀。以 整體性 能 觀 之 ， 此 實施例比上述其他上述之變化例較不常被使用 1 ° 若金屬發泡被選擇做爲多孔性流動 體之材 料 金 屬 發 泡與第二流體之間的熱傳遞很高，由 於對已 知 體 積 而 言 其熱交換表面積很大之故，不再成爲限制因素 ：〇 但是，由金屬發泡製成之流動體由 於多孔 性 之 故 y 其 熱傳遞很低，多孔性亦對流動體與流 ,路外壁 之 間 的 熱 傳 遞有負面效果。在發泡中逐漸增加金 屬之量 會 導 致 這 兩 個互成對立因素之整體效果的改善。 可使用具有高熱傳導係數之如銅的 金屬所 製 成 之 金 屬 發泡。流動體最好亦從具有高熱傳導 及熱傳 遞 之 金 屬 如銅所製成，其他適宜之金屬包括銥 ，銀， 鎳 及 不 銹 鋼 。用來生產金屬發泡之開始材料最好 爲塑膠 發 泡 如 聚 醯胺，聚酯，或具有開放互連細孔的 網狀的 聚 酯 ， 並 且 有恆定之PPI値。細孔之直徑最好在 400-1500 微 米 之 範 圍內，更佳爲在800- 1 200微米。體積 :梯度可 爲 在 流 體 之 流動方向上通過發泡從小於5%升到超 過95% 〇 沉 積 在 塑 膠發泡上之金屬厚度最好其梯度之範 圍最好 在 流 動 am 體 之 流入側爲5 - 1 0微米，到最好在流路之 -7- 附近爲 30-70 微 米 502103 五、發明說明（6) ，例如各爲8微米及42微米。此種金屬發泡可在適宜之 電解槽中使銅在聚合物發泡之基材上電鑄，之後並選擇 性地進行聚合物之裂解而很容易形成。若需要的話，薄 的電導層例如銅層可以使用其他技術，例如（磁控管）物 理氣相沉積法，化學氣相沉積法等而首先沉積在發泡上 ，之後此薄層可進一步地在電解槽中成長。 許多焊接技術（感應，擴散）及熔接技術可被用來將金 屬發泡固定到流路上。含有錫之熔焊合金特別適合用於 銅發泡中。 本發明之熱交換器最好爲模組化構造，故多數個模組 可被結合而形成較大的單元。 本發明亦是關於一種熱泵，例如一種熱音轉換裝置， 如申請專利範圍第1 1項所述用來轉換能量之用，其中使 用本發明之熱交換器。用來壓縮及移動氣態流體之馬達 爲’例如一個封閉音學共振電路。所用之再生器最好具 有一個層狀構造，包括具有傳導性較差之金屬的發泡層 。此種熱音轉換裝置之例子，包括熱音之熱引擎，及熱 音馬達。 附圖之簡單說明 下面，本發明將參照附圖詳細說明，其中： 第1圖習知技術之熱交換器的實施例之立體圖； 第2圖是顯示本發明熱交換器的第丨實施例之立體圖 502103 五、發明說明（7) 第3圖是顯示本發明熱交換器的第2實施例之立體圖 第4圖是顯示如申請專利範圍第3項之熱交換器模組 之立體圖； 第5圖是顯示本發明熱交換器的第3實施例之立體圖 第6圖用來做能量轉換用之熱-音轉換裝置之槪圖，其 中使用有本發明之熱交換器。 發_明較佳實施例之胃羊种設昍 在第1圖顯示之習知技術的熱交換器1 〇之實施例中， 許多例如由銅製成之管狀流路1 2被配置成彼此平行。通 過流路1 2之第一流體的流動方向以單一箭頭顯示，是顯 示由頂部向下之情況。流路1 2之入口端1 4通常彼此由 分配器蓋之助（圖中未顯示）而彼此連接。出口端1 6彼此 亦以相同方式連接。第二流體之一個多孔性流動體整體 以符號20代表，其包括有許多金屬帶22，其被配置成彼 此隔開一個距離而且彼此平行，並且每一個具有一個金 屬發泡層24位於其之間。流路1 2之孔被設置在金屬帶 22及金屬發泡層24中之適當位置。金屬帶22被熔接到 流路12之外壁26上。流動體20被配置在容室或外殼中 (圖中未顯示），其設置有一個第二流體之進給及排出及 分配器裝置（若需要時）。熱交換器1 0之外殼側可設置有 聯結裝置，使多數個熱交換器可依照所需要而彼此聯結 502103 五、發明說明（8) 〇 第2圖顯不有本發明熱交換器的較佳實施例，其中與 第1圖相同的元件付予相同的符號。 熱交換器1 0包括許多平行的流路1 2，被配置成彼此隔 開一個距離，且具有橢圓形剖面，如爲液體之一種第一 流體可被引導通過其中。流動體20包括兩個金屬發泡部 份3 0及32，每一個具有平行於第二流體，如氣體之流動 方向上之體積密度之梯度。爲了簡化此圖，具有最高體 積密度之表面在此圖及下面之圖中以厚實線表示之。在 部份30中，體積密度（金屬之量）在第二流體之流動方向 上增加，而在部份3 2中，體積密度在所顯示之流動方向 上減少。故，大部份金屬存在於流路1 2之中間附近，而 在此亦有最高之熱通量密度。流動體20之外表面尤其是 流入側（及排出側）爲相當開放。 第3圖顯示另一實施例，其中爲矩形剖面之流路1 2被 配置在流動體20之部份40之間。每個部份40包含有兩 個金屬發泡層42，其具有最高體積密度之表面結合兩個 配置成彼此鄰接之流路1 2的外壁44，而具有最低體積密 度之表面則彼此互相抵住。在此圖中，部份40之兩個金 屬發泡層42之間的分離表面以虛線表示。第4圖顯示第 3圖之本發明熱交換器實施例之模組。 第5圖顯示本發明熱交換器另一變化例，其中設置有 六個交互堆疊之金屬發泡層50被用來做爲流動體20,其 -10- 502103 五、發明說明（9) 梯度在被引導通過流路1 2之第一流體的流動方向上看時 ，可交互地反覆增加或減少。 第6圖顯示本發明熱泵之外觀槪圖，在此情形中用來 做能量轉換用之熱-音轉換裝置60之實施例最好使用本 發明之熱交換器。 此裝置60包括一個充滿氣體之聲音或聲音-機械共振 電路62，其具有例如由鎳發泡製成之再生器64，被配置 在本發明之兩個熱交換器10之間。若裝置60被做爲熱 泵之時，機械能例如經由薄片以電動線性馬達協助而振 動之下，被輸送到氣體。其他可能方式包括，風箱或自 由活塞構造。被振動且做爲第二流體用之氣體將熱從第 一熱交換器1 〇之第一流體經由再生器抽出到第二熱交換 器1 0之中，在此熱被傳遞到第三流體。依此方式，可將 熱從設定在低溫流體之流動傳遞到高溫之流體中。周期 性壓力變動及此程序所需之氣體位移可在高功率音波之 影響下，於封閉之共振電路62中產生。在此點，須提及 者，壓力振幅是比在一般自由空間中者大好幾倍，亦即 爲在此系統中平均壓力之1 〇%大小級數。 若轉換裝置被用來做爲馬達，熱被輸送到高溫下之熱 交換器，並且由另一個低溫’例如周遭溫度之熱交換器 散熱，使其振動可被維持。若比需要維持振動之更多的 熱被輸送時，一聲能可從共振器中抽出而做爲有用的輸 出。 -11- 502103 :鳥'外:.·”ι ---]__ϊίΑ_ 五、發明說明（10) 本發明熱交換器之性能將根據下列例子做更詳細地解 釋。 · 許多熱交換器被生產且進行測試。第一熱交換器A之 多孔性流動體是由長度爲90公厘寬度爲1 2公厘之銅發 '泡（每英吋6 5 ?L )帶所製成。孔被衝出以做爲流路。流路 包括9個外徑爲6,公厘之小銅管（內徑爲4公厘）以固定 間隔配置。第二流體之有效流路爲90公厘X 70公厘。在 小銅管之入口端及出口端·之多歧管個被連接到水進給管 及水排出管。 在第二熱交換器B中，使用一個由相同銅發泡體製成 之流動體，但是厚度爲0.25公厘之青銅薄片可被配合到 此熱交換器中。發泡體及薄片可在爐中被熔焊在一起爲 了防止金屬發泡體在熱之影響下封閉在一起，銅發泡體 及青銅薄片亦可被一個一個地被熔焊到小銅管上。 在第三熱交換器C中，流動體僅包括3 9個青銅薄片。 在本發明之第四熱交換器D中，如第2圖所示’具有 與熱交換器A - C相同之尺寸及管數，流動體包括兩個銅 發泡體層，其乃在室溫下在具有800微米細孔直徑之PU 發泡體上，於成分爲硫酸銅=250克/升，硫酸=70克/升 ，氯離子C1·二15毫克/升，且pH^O·!’電流密度在5女 培/平方公寸之條件下被製成。在裂解之後’依照此方式 生產之銅發泡體層在一側上具有8微米之金屬厚度’而 在另一側上沉積之金屬厚度爲42微米。相當於小銅管直 -12- 502103 91· 7> 1:9 修正 j ---^——-----五、發明說明（11 ) .一 徑之半的凹處被設置在這些發泡層之後者提到之側上， 在其後方小銅管被置於這些凹處中。錫焊被使用做爲接 合技術。 這些熱交換器被用來進行試驗，其中一個量之熱水（丁= 約8 0 °C )使用流量計控制經由靜熱槽中通過小銅管而被計 算。一個離心泵賤·用來吸入空氣使之通過熱交換器之流 動體，其被置於流路中。被吸入之空氣體積使用流量計 在熱交換器與離心栗之間進行測量。通過流動體之壓力 降及包含水之第一流體之入口溫度T,及出口溫度τ2，及 包含空氣之第二流體之出口溫度τ3被測量。被空氣流所 吸收之熱Q可使用下列公式而從水之體積流量Fw(升/分） ，及水之進入及出去之溫度差（TpTJ所計算。 Q = Ww · (T丨-T2) · Fw/60[W] 其中Ww是水之熱容量（4180J · Kg · K·1 )。此試驗在許 多不同空氣速度之下進行。雷諾數（Reynolds number)是 從在熱交換器所在位置所測量之氣體速度，以及對所有 熱交換器A-D之液壓直徑DH =0.0033所決定。黏度値施加 於吸入新鮮空氣之氣體溫度’其溫度亦同樣地被測量。 氣體側之努協爾特數（N u s s e 1 t n u m b e r )可由去除液體側 之熱傳遞，並且假設爲擾流管之情況下計算之： NuUe>Q · DH/人· △ L，其中Aw爲總熱交換表面積’而 △I爲氣體與熱交換器之間的溫度差。 如在專業領域所通用者’熱傳遞以Re之關係被表示爲 -1 3 - 103五、發明說明（12) 以=!^.1^-1.?厂1/3，其中？1*爲普朗特數，其在空氣 之情況爲0 . 7。 所謂的摩擦係數可由相同方式，由所測量已知尺寸之 這些熱交換器的壓力降及所測量之速度而計算出來，並 且可以雷諾數之涵數表示之： f = Α〇Δ p/ Aw ( 1 /2 p v2) 下表顯示不同之熱交換器A-D且Re = 3 00之時，熱傳 遞（〕Η)，摩擦係數（f)及比率jH/f之結果。 表 熱交換器 JH f jH/f A 0.07 20 0.004 B 0.7 40 0.018 C 0.03 1 .4 0.021 D 0.5 15 0.033 由上表可知，如所預料地熱交換器A(僅有發泡體）比熱 交換器C (僅有薄片）可提供較高的熱傳遞。但是，流動阻 抗非成正比例地增加。再者，可看出雖然熱交換器B(發 泡體及薄片）比本發明之熱交換器D可達到較高的熱傳遞 ，但是其流動阻抗很高。本發明之熱交換器具有最佳之 整體性能，以jH/f表示。從此可知，使用具有適當之金 屬分佈及改變此金屬量之發泡體之時，可達成在一方面 之熱傳遞/傳導，與另一方面之流動阻抗之間的最有利平 衡。 -14- 502103 五、發明說明（13) 元件之符號說明 1〇 習知技術的熱交換器 12 流路 14 入口端 16 出口端 24 金屬發泡層 22 金屬帶 20 多孔性流動體 26 外壁 40 部份 42 金屬發泡層 44 外壁 50 金屬發泡層 60 熱-音轉換裝置 62 音響-機械共振電路 64 再生器 -15--4- 502103 V. Description of the invention (3) Foam is arranged in the flow path. If necessary, the pore size in this foaming can be changed, that is, the number of pores can be changed. SUMMARY OF THE INVENTION The general purpose of the present invention is to improve the overall performance, that is, the relationship between the heat transfer and the flow resistance of the above-mentioned heat exchanger. In the above type of heat exchanger, the metal foam according to the present invention has a gradient in metal bulk density. The use of this metal foam with a gradient in metal bulk density makes the volume density of the foam, that is, the amount of metal can be suitable for the area's heat flux density and flow resistance while the number of pores (PPI) remains the same . In metal foaming, the heat flux density is highest in the vicinity of the flow path, so that the metal foaming at this position must contain more metal than the outer periphery of the fluid, but its heat flux density is much lower. This is because the metal bulk density of the metal foam used is changed. According to the present invention, the metal foaming arrangement of the heat exchanger has the effect of promoting heat transfer from the metal foaming to the wall of the flow path. When the PPI remains the same, and when the thickness of the metal limbs separating the pores remains the same, the metal volume gradient in the metal foam is more effective than changing the number of pores. Such a metal foam having a bulk density gradient can be made, for example, by an electroplating method on a plastic foam in an electrolytic cell, as will be explained in detail below. It should be mentioned that the FR-A-2 766 967 patent has disclosed a heat sink for electronic components, which includes a metal foam with deposited metal, which has a thickness in the thickness direction of the foam. Gradient 502103 V. Description of the invention (4) (gradient). Because in this production method, the foam density changes in one direction, the fluid body preferably includes at least two layers of metal foam, and the surfaces of the layers having the same volume density face each other. This can provide many embodiments of the fluid with application advantages. In the first embodiment, the bulk density of the metal foam increases from the inflow side of the flowing body of the second fluid toward the flow path, so that more metal is generated where the heat flux density is larger. The shape of the flow path is not absolutely critical. Round tubes, flat hollow tubes, etc. can be used. However, in order to limit the flow resistance, the shape of the flow path is preferably matched to the flow shape of the second fluid. It is advantageous when the flow path has an elliptical section, and its main axis extends in the direction of flow of the second fluid. This shaped flow path can be combined with a large heat exchange surface area with low flow resistance. The flow then advantageously comprises two layers of metal foam, preferably having the same number of pores per linear inch (PPI), with the sides having the highest metal bulk density facing each other. On these sides, recesses in the flow path are provided. According to another preferred embodiment, in particular, its simple modular structure is advantageous. The flow path includes a tubular body with a rectangular cross section, and it is separated by a portion of the flow body. The bulk density of the portion of the flow body is It is highest near the outer wall of the flow path. The module of this preferred embodiment of the heat exchanger may include, for example, a flow path of a rectangular cross section, two opposite walls of which are provided with a layer of metal foam, of which the surface of the layer with the highest bulk density is under discussion 502103 2. Description of invention (5). If the heat exchanger is more similar to a heat exchanger with a flowing body containing metal foamed sections separated by sheets, the most desirable one is to use a plurality of layers of metal foaming whose gradient of bulk density is parallel to the first The direction of flow of a fluid is preferably interactive. In terms of overall performance, this embodiment is less commonly used than the other above-mentioned variations. If metal foam is selected as the material of the porous fluid, the heat transfer between the metal foam and the second fluid is very low. High, due to its large heat exchange surface area for a given volume, it is no longer a limiting factor: 〇 However, fluids made from metal foams have low heat transfer and porosity due to their porosity It also has a negative effect on the heat transfer between the flowing body and the flow and the outer wall of the road. Gradually increasing the amount of metal in foaming will lead to an improvement in the overall effect of these two opposing factors. Metal foams made of metals such as copper with high thermal conductivity can be used. The fluid body is also preferably made of a metal with high heat transfer and heat transfer, such as copper. Other suitable metals include iridium, silver, nickel, and stainless steel. The starting materials used to produce metal foams are preferably plastic foams such as polyamides, polyesters, or meshed polyesters with open interconnected pores, and have a constant PPI 値. The diameter of the pores is preferably in the range of 400-1500 micrometers, and more preferably in the range of 800-1 200 micrometers. Volume: The gradient can be raised from less than 5% to more than 95% by foaming in the direction of fluid flow. The thickness of the metal deposited on the plastic foam is preferably the range of the gradient is 5 on the inflow side of the flowing am body. -10 microns, preferably 30-70 microns in the vicinity of -7- of the flow path 502103 V. Description of the invention (6), for example, 8 microns and 42 microns each. Such metal foaming can be easily formed by electroforming copper on a polymer foamed substrate in a suitable electrolytic cell, and then selectively cracking the polymer. If necessary, a thin conductive layer such as a copper layer can be deposited on the foam first using other techniques, such as (magnetron) physical vapor deposition, chemical vapor deposition, etc., and then the thin layer can be further deposited on Growing in an electrolytic cell. Many welding techniques (induction, diffusion) and welding techniques can be used to fix the metal foam to the flow path. Tin-containing solder alloys are particularly suitable for use in copper foaming. The heat exchanger of the present invention is preferably a modular structure, so a plurality of modules can be combined to form a larger unit. The present invention also relates to a heat pump, such as a thermal sound conversion device, for converting energy as described in item 11 of the scope of patent application, wherein the heat exchanger of the present invention is used. The motor used to compress and move the gaseous fluid is, for example, a closed acoustic resonance circuit. The regenerator used preferably has a laminar structure, including a foamed layer with a less conductive metal. Examples of such thermal sound conversion devices include thermal sound heat engines and thermal sound motors. Brief description of the drawings In the following, the present invention will be described in detail with reference to the accompanying drawings, in which: FIG. 1 is a perspective view of an embodiment of a heat exchanger of a conventional technology; FIG. Perspective view 502103 V. Description of the invention (7) Figure 3 is a perspective view showing a second embodiment of the heat exchanger of the present invention. Figure 4 is a perspective view showing a heat exchanger module such as item 3 of the scope of patent application; Figure 5 FIG. 6 is a perspective view showing a third embodiment of the heat exchanger of the present invention. FIG. 6 is a schematic diagram of a heat-sound conversion device used for energy conversion, in which the heat exchanger of the present invention is used. Development of Gastric Sheep Breeding in the Preferred Embodiment In the embodiment of the conventional heat exchanger 10 shown in FIG. 1, many tubular flow paths 12 made of copper, for example, are arranged parallel to each other. The flow direction of the first fluid passing through the flow path 12 is shown by a single arrow, and it is shown from the top to the bottom. The inlet ends 14 of the flow paths 12 are usually connected to each other with the help of a distributor cover (not shown). The outlet ends 16 are also connected to each other in the same manner. A porous fluid body of the second fluid is represented as a whole by the symbol 20, which includes a plurality of metal bands 22, which are configured to be spaced apart from each other and parallel to each other, and each has a metal foam layer 24 therebetween. . The holes of the flow path 12 are provided at appropriate positions in the metal tape 22 and the metal foam layer 24. The metal strip 22 is welded to the outer wall 26 of the flow path 12. The fluid body 20 is arranged in a container or a casing (not shown in the figure), and is provided with a second fluid feed and discharge and distributor device (if necessary). The shell side of the heat exchanger 10 can be provided with a coupling device, so that most heat exchangers can be connected to each other as required. 502103 5. Description of the invention (8) 〇 Figure 2 shows that the heat exchanger of the present invention is not better. In the embodiment, the same components as those in FIG. 1 are assigned the same reference numerals. The heat exchanger 10 includes a plurality of parallel flow paths 12 configured to be spaced apart from each other and having an elliptical cross-section through which a first fluid, such as a liquid, can be guided. The fluid body 20 includes two metal foaming portions 30 and 32, each having a gradient parallel to the bulk density in the direction of flow of a second fluid, such as a gas. To simplify this figure, the surface with the highest volume density is shown as a thick line in this figure and in the figures below. In section 30, the bulk density (amount of metal) increases in the flow direction of the second fluid, and in section 32, the bulk density decreases in the flow direction shown. Therefore, most of the metal exists near the middle of the flow path 12, and also has the highest heat flux density here. The outer surface of the fluid body 20, especially the inflow side (and the discharge side), is relatively open. Fig. 3 shows another embodiment in which the flow path 12 having a rectangular cross section is arranged between the portions 40 of the fluid body 20. Each part 40 includes two metal foam layers 42 whose surfaces with the highest bulk density are combined with two outer walls 44 which are arranged adjacent to each other, and the surfaces with the lowest bulk density abut each other. . In this figure, the separation surface between the two metal foam layers 42 of the portion 40 is shown by a dotted line. Fig. 4 shows a module of an embodiment of the heat exchanger of the present invention shown in Fig. 3. Fig. 5 shows another variation of the heat exchanger of the present invention, in which six alternately stacked metal foamed layers 50 are used as the flow body 20, and its -10- 502103 V. Description of the invention (9) The gradient is When viewed in the direction of flow of the first fluid guided through the flow path 12, it may alternately increase or decrease repeatedly. Fig. 6 is a diagram showing the appearance of a heat pump according to the present invention. In this case, the embodiment of the heat-sound conversion device 60 used for energy conversion preferably uses the heat exchanger of the present invention. This device 60 includes a gas-filled sound or sound-mechanical resonance circuit 62 having a regenerator 64 made of, for example, nickel foam, disposed between two heat exchangers 10 of the present invention. When the device 60 is used as a heat pump, the mechanical energy is delivered to the gas, for example, by the vibration of a sheet with the assistance of an electric linear motor. Other possibilities include bellows or free piston construction. The gas that is vibrated and used as the second fluid draws heat from the first fluid of the first heat exchanger 10 through the regenerator to the second heat exchanger 10, where the heat is transferred to the third fluid. In this way, heat can be transferred from a fluid set at a low temperature to a fluid set at a high temperature. Periodic pressure fluctuations and the gas displacement required for this procedure can be generated in a closed resonance circuit 62 under the influence of high-power sound waves. At this point, it must be mentioned that the pressure amplitude is several times larger than that in general free space, that is, the magnitude of the average pressure in this system is 10%. If the conversion device is used as a motor, the heat is transferred to a heat exchanger at a high temperature and is dissipated by another heat exchanger at a low temperature, such as the ambient temperature, so that its vibration can be maintained. If more heat is transferred than is necessary to maintain vibration, a sound energy can be extracted from the resonator as a useful output. -11- 502103: Birds' outside:. · ”Ι ---] __ ϊίΑ_ V. Description of the invention (10) The performance of the heat exchanger of the present invention will be explained in more detail according to the following examples. · Many heat exchangers are produced and The test is performed. The porous fluid body of the first heat exchanger A is made of a copper hair bubble (65 5 L per inch) with a length of 90 mm and a width of 12 mm. The holes are punched out. It is used as a flow path. The flow path includes nine small copper pipes with an outer diameter of 6 mm (inner diameter of 4 mm) arranged at fixed intervals. The effective flow path of the second fluid is 90 mm X 70 mm The multiple manifolds at the inlet and outlet ends of the small copper tubes are connected to the water inlet and outlet pipes. In the second heat exchanger B, a flow made of the same copper foam is used Bronze sheet with a thickness of 0.25 mm can be fitted into this heat exchanger. The foam and sheet can be welded together in a furnace in order to prevent the metal foam from being closed together under the influence of heat. The copper foam and the bronze sheet can also be welded to the small copper tubes one by one. In the third heat exchanger C, the fluid body includes only 3 9 Bronze sheet. In the fourth heat exchanger D of the present invention, as shown in FIG. 2 'has the same size and the same number of tubes as the heat exchangers A to C, the fluid includes two copper foam layers, which are At room temperature on a PU foam with a pore diameter of 800 microns, the composition is copper sulfate = 250 g / L, sulfuric acid = 70 g / L, chloride ion C15 · 15 mg / L, and pH ^ O · 'The current density was made at 5 females per square inch. After the cracking, the copper foam layer produced in this way had a metal thickness of 8 microns on one side and was deposited on the other side. The metal thickness is 42 microns. It is equivalent to a small copper tube straight -12-502103 91 · 7 > 1: 9 correction j --- ^ --------- V. Description of the invention (11). Recesses are placed on the sides mentioned after the foamed layers, and behind them small copper tubes are placed in these recesses. Soldering is used as the joining technique. These heat exchangers were used for testing, One of the quantities of hot water (D = about 80 ° C) is calculated using a flow meter control through a small copper tube in a static and thermal tank. A centrifugal pump is cheap The air flowing in through the heat exchanger is placed in the flow path. The volume of air sucked in is measured using a flow meter between the heat exchanger and the centrifugal pump. The pressure drop through the fluid and the water containing The inlet temperature T of the first fluid, and the outlet temperature τ2, and the outlet temperature τ3 of the second fluid containing air are measured. The heat Q absorbed by the air flow can be calculated from the volume flow rate Fw (liters / minute) of water using the following formula ), And the temperature difference between water entering and leaving (calculated by TpTJ. Q = Ww · (T 丨 -T2) · Fw / 60 [W] where Ww is the heat capacity of water (4180J · Kg · K · 1). This test is performed at many different air speeds. The Reynolds number is determined from the gas velocity measured at the heat exchanger location and the hydraulic diameter DH = 0.0033 for all heat exchangers A-D. Viscosity 温度 The temperature of the gas applied to the fresh air inhalation ' The temperature is also measured. Nusse 1 tnumber on the gas side can be calculated by removing the heat transfer on the liquid side and assuming a spoiler: NuUe> Q · DH / person · △ L, where Aw is the total heat Exchange surface area 'and ΔI is the temperature difference between the gas and the heat exchanger. As commonly used in the professional field, the heat transfer is expressed by the relationship of Re as -1 3-103. V. Description of the invention (12) With =! ^. 1 ^ -1.? Factory 1/3, where? 1 * is the Prandtl number, which is 0.7 in the case of air. The so-called friction coefficient can be calculated in the same way from the measured pressure drop of these heat exchangers of known size and the measured speed, and can be expressed by the Reynolds number's nominal: f = Α〇Δ p / Aw ( 1/2 p v2) The following table shows the results of heat transfer (] Η), friction coefficient (f), and ratio jH / f when different heat exchangers AD and Re = 3 00. Table heat exchanger JH f jH / f A 0.07 20 0.004 B 0.7 40 0.018 C 0.03 1. .4 0.021 D 0.5 15 0.033 As can be seen from the table above, as expected, heat exchanger A (only foam) is better than heat exchanger C (Sheet only) Provides higher heat transfer. However, the flow impedance increases non-proportionally. Furthermore, it can be seen that although the heat exchanger B (foam and sheet) can achieve higher heat transfer than the heat exchanger D of the present invention, its flow resistance is high. The heat exchanger of the present invention has the best overall performance, expressed in jH / f. It can be seen from this that the most favorable balance between heat transfer / conduction on the one hand and flow resistance on the other hand can be achieved when using a foam with an appropriate metal distribution and varying the amount of this metal. -14- 502103 V. Description of the invention (13) Symbol description of the components 10 Heat exchanger 12 of the conventional technology 12 Flow path 14 Inlet end 16 Outlet end 24 Metal foam layer 22 Metal strip 20 Porous fluid 26 Outer wall 40 Parts 42 metal foam layer 44 outer wall 50 metal foam layer 60 thermal-sound conversion device 62 acoustic-mechanical resonance circuit 64 regenerator-15-